GATE AG 2015 • Q46 NAT • 2 Marks

Section 3: Farm Power

Farm Power

Subtopic: Thermodynamic principles of I.C. engines

Question Statement:

If an irrigation water source has the concentrations of Na⁺, Ca⁺⁺ and Mg⁺⁺ as 28, 10 and 5 milliequivalents per litre, respectively, then the Sodium adsorption ratio of this water is _____.

Official Answer Key:

10.2 to 10.4

Step-by-Step Solution & Explanation

SAR = Na⁺ / √[(Ca⁺⁺ + Mg⁺⁺)/2] (concentrations in meq/L). SAR = 28/√[(10+5)/2] = 28/√7.5 = 28/2.7386 = 10.23. This lies within the accepted range 10.2–10.4.

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